Figure 12b. Pulmonary artery sling. (a) On a CT scan, the left pulmonary artery (*) originates aberrantly from the proximal right pulmonary artery and crosses the midline between the trachea (arrow) and the esophagus (arrowhead). An associated tracheal ring is also seen. (b) VR image (posterior view) shows the characteristic course of the aberrant left pulmonary artery (*).